Creep instability rock burst mechanism of high-stress isolated coal immersed in water

Abstract

Based on the rock burst occurrence of the south water sump connecting roadway in the seventh mining area of Zhaolou Coal Mine, the mechanism of creep instability rock burst of high stress isolated coal immersed in water was studied by means of theoretical analysis, numerical simulation and field measurement. The main conclusions are as follows: the bearing stress of isolated coal immersed in water mainly presents the creep evolution law from “bimodal-shaped” to “saddle-shaped”, then to “platform-shaped” and finally to “unimodal-shaped”. Based on the burgers model, a water damage variable was introduced to establish a mechanical model for estimating the concentrated stress in the elastic zone of isolated coal, revealing the creep instability impact mechanism of high stress isolated coal immersed in water. Under the continuous weakening effect of water accumulation in the mine sump, the strength of isolated coal gradually decreases until residual strength, and the bearing capacity also decreases, leading to the transfer of stress concentration from the plastic zone to the elastic zone. When the concentrated stress in the elastic zone exceeds its instability threshold, it is easy to induce rock burst. Based on this, the prevention and control measures for the creep instability impact of high stress isolated coal immersed in water were proposed: reducing the average bearing stress of the isolated coal, increasing the comprehensive compressive strength of the isolated coal, and filling the tunnels near the isolated coal when necessary.

Keywords

• rock burst
• high ground stress
• isolated coal immersed in water
• creep instability
• stress distribution